Method for the production of primary amines by hydrogenating nitriles

ABSTRACT

The present invention relates to an improvement in a process for preparing primary amines by hydrogenating nitrites. The improvement in the hydrogenation process is that a hydrogenation catalyst modified ex situ with preadsorbed alkali metal carbonate or hydrogencarbonate such as K 2 CO 3  or KHCO 3  is used.

The present invention relates to the preparation of primary amines bycatalytically hydrogenating nitrites.

Hydrogenation of nitrites to produce amines is of great industrialimportance owing to the wide-ranging applications of amines, such as theorganic solvents, agrochemicals, pharmaceuticals, surfactants, andespecially, the intermediate of nylon-6,6. The hydrogenation is usuallycarried out over Raney nickel catalyst in the liquid phase at elevatedtemperatures and hydrogen pressures, in which the ammonia is present toenhance the yield of the primary amine by inhibiting the formation ofthe secondary and tertiary amines.

Representative patents and articles illustrating the hydrogenation ofnitrites to produce primary amines are as follows:

E. J. Schwoegler and H. Adkins, J. Am. Chem. Soc. 61, 3499 (1939)predicted and then demonstrated that adding sufficient ammonia to thehydrogenation of a nitrile would strongly inhibit the formation ofsecondary amine and thus greatly improve the selectivity to primaryamine.

U.S. Pat. No. 2,165,515 discloses a process for the production ofprimary amines by the catalytic hydrogenation of nitrites using cobaltand cobalt promoted with barium or manganese.

S. Sakakibara et al., J. Chem. Soc. Japan, Ind. Chem. Sect., 56, 497(1953) describe a method for preparing primary amines such asdodecylamine by the hydrogenation of nitrites such as lauronitrile withammonia using Raney nickel catalyst.

U.S. Pat. No. 3,574,754 discloses a process for preparing primary aminesby the hydrogenation of nitriles with ammonia using Raney nickelcatalyst.

U.S. No. 4,739,120 discloses a process for the hydrogenation of nitritesto primary amine using a rhodium catalyst. The reaction is carried outin the presence of a two-phase solvent system comprising an aqueousphase and a water-immiscible organic phase.

M. Besson et al., Stud. Surf. Sci. Catal., Vol. 59, “HeterogeneousCatalystis and Fine Chemicals II”, ed. M. Guisnet et al., 1991, pp.113-120, reported a method for the production of primary amines fromnitrites in the presence of cyclohexane, utilizing a Raney nickelcatalyst doped with molybdenum or chromium.

EP Pat. No. 0,547,505 discloses a process for the production ofdodecylamine by the catalytic hydrogenation of lauronitrile in thepresence of ammonia using magnesium-nickel catalyst coprecipitated on asupport.

Pol. Pat. No. 51,530 employed nickel catalyst to hydrogenate aliphaticnitrites and especially lauronitrile. Ammonia was present to suppressthe production of secondary amine.

JP Pat. No. 7,941,804 discloses a process for producing primary aminesby hydrogenating the nitrile in lower alcohol and cyclic hydrocarbonmixtures in the presence of alkali or alkali earth metal hydroxides andchromium modified Raney nickel catalyst.

JP Pat. No. 6,032,767 discloses a process for the hydrogenation ofnitrites to primary amine using a Raney nickel catalyst in the presenceof ammonia.

D. Djaouadi et al., Catal. Org. Reactions, 423 (1995) prepared achromium and iron doped Raney nickel catalyst by alkali leaching ofintermetallic alloys, Ni₄₀Al₆₀ or Ni₂₅Al₇₅ being the parent alloys. Theselective hydrogenation of valeronitrile to the corresponding primaryamine was performed in cyclohexane using a stirred autoclave. Theimprovement in selectivity to the primary amine with doping is mainlyexplained by a decrease of the rate of hydrogenation of the intermediatesecondary imine, thus favoring reverse reactions.

S. Xie et al., Appl. Catal. A: General, 189, 45 (1999) reported theammonia additive could greatly improve its selectivity to primary aminein the selective hydrogenation of stearonitrile over Ni—B/SiO₂ amorphouscatalysts, although a slight decrease in the activity was observed. Theamorphous structure of the catalyst and the alloying boron played keyroles in promoting the hydrogenation activity and the selectivity toprimary amines. However, no significant promoting effect of KNO₃ dopedSiO₂ was observed.

Alkali metal hydroxide additives are also used to improve theselectivity in the hydrogenation of organic nitrites to amines. T. A.Johnson et al., Proceedings of the “18th Conference on Catalysis ofOrganic Reactions” ed. M. E. Ford, 2000, paper 13, reported that theselective hydrogenation of nitrile could be carried out using lithiumhydroxide modified sponge nickel and cobalt catalysts.

U.S. Pat. No. 5,874,625 discloses a process for the catalytichydrogenation of organic nitrites to primary amines using a slurry ofRaney nickel catalyst and aqueous alkali metal hydroxide, wherein theRaney nickel catalyst and aqueous alkali metal hydroxide contribute fromabout 0.1 to about 3% water. The autoclave charge is pressurized withhydrogen, and then heated to a final temperature of about 110° C.

U.S. Pat. No. 5,777,166 discloses a process for the hydrogenation ofnitriles to amines. The process comprises: a) doping a Raney nickel typecatalyst with at least one additional metal element selected from GroupIVb of the Periodic Classification of the Elements which is derived froman Ni/Al/doping element metallurgic precursor alloy and wherein thedoping element/Ni ratio by weight is between 0.05 and 10%; and b)exposing the catalyst to a nitrile in a liquid reaction medium whichdissolves the nitrile along with at least one inorganic base selectedfrom the group consisting of LiOH, NaOH, KOH, RbOH, and CsOH and therebyhydrogenate the nitrile.

U.S. Pat. No. 5,869,653 discloses a process for the catalytichydrogenation of nitrites which comprises contacting the nitrile withhydrogen in the presence of a sponge cobalt catalyst under ammonia-freeconditions for effecting conversion of the nitrile group to the primaryamine, the improvement in the hydrogenation process which resides ineffecting the hydrogenation in the presence of a sponge cobalt catalysttreated with a catalytic amount of lithium hydroxide and effecting thereaction in the presence of water.

WO-01/66511 discloses a process for hydrogenating nitriles to amines,although no modification of the hydrogenation catalyst takes placebefore the hydrogenation.

Alkali metal carbonates were also used for promoting the selectivity ofRaney nickel catalysts for the preparation of amines in the alkylationof ammonia or alkylamines with alcohols. French Pat. No. 2,351,088, Ger.Offen. No. 2,621,449, Ger. Offen. No. 2,625,196 and Ger. Offen. No.2,639,648 disclose the preparation of tertiary amines by alkylation ofsecondary amines by alcohols with water removal in the liquid phase inthe presence of hydrogenation-dehydrogenation catalyst such as Raneynickel or Raney cobalt and one or more basic alkali metal or alkaliearth metal compounds. Thus a mixture of 774 kg n-dodecanol, 500 kgethylbenzene, 10 kg Na₂CO₃, and 300 kg Raney nickel was heated to 130-5°C., hydrogen and dimethylamine were fed into the mixture withazeotroping of water until the theoretical amount of H₂O was removed,and the catalyst was filtered off and the filtrate distilled to give 80%RNMe₂, 15% R₂NMe, and 5% R₃N (R=n-dodecyl).

Ger. Offen. No. 2,645,712 discloses a process for the preparation ofsecondary amines by alkylation of ammonia by alcohols in the presence ofhydrogenation-dehydrogenation catalyst and a basic alkali or alkaliearth metal compound. Thus ammonia was fed at atmospheric pressure intoa dephlegmator reactor containing stearyl alcohol, Raney nickel, andNa₂CO₃ at 90-140° C. with continuous removal of H₂O to give >95%distearylamine.

Kalina, M. and Pashek, Yu. (Kinetika i Kataliz, 10, 574, 1969) reportedon the use of Na₂CO₃ modified metallic cobalt and nickel catalysts forthe liquid phase hydrogenation of palmitic nitrile. The addition ofsodium carbonate to the reaction mixture at Na₂CO_(3/)catalyst/nitrile5/5/100 weight ratio, 150° C. and 50 bar hydrogen pressure resulted in adecrease of secondary amine selectivity. The selectivity of thesecondary amine measured at 50% conversion on Co, Ni, Co+Na₂CO₃,Ni+Na₂CO₃ catalysts was 17.4, 20.1, 11.0 and 12.2%, respectively.

A catalyst system containing supported nickel and alkaline carbonate wasused for the preparation of dissymmetric aliphatic secondaryalkylamines.

U.S. Pat. No. 5,254,736 and EP Pat. No. 0 526 318 disclose a process forthe preparation of secondary methylalkyl amines of general formula:R—NH—CH₃, in which R is C₁₀-C₂₂ aliphatic chain, by amination reactionbetween an alcohol and a monoalkylamine. The amination reaction wascarried out with a supported nickel catalyst in the presence of analkali carbonate, potassium carbonate being the best, the weight ratiobetween the potassium carbonate and the nickel catalyst being between1:4 and 1:1, under a hydrogen pressure between 10 and 50 bar. In atypical example 422 g dodecylamine (2.3 moles), 1460 g methanol (45moles), 38.6 g supported nickel catalyst (Harshaw Ni 1404T), and 57.1 gK₂CO₃ were autoclaved at 180° C., 40 bar hydrogen pressure and 1800 rpmfor 6 hours. The composition of the reaction product was 0% RNH₂, 85.9%RNHMe, 1.3% RNMe₂, 6.0% R₂NH, and 6.8% ROH, whereas on the unmodifiedcatalyst the concentrations were 15.0%, 17.2%, 44.9%, 13.8%, and 9.1 %,respectively (R=n-dodecyl, Me=methyl).

The drawbacks to the previous processes disclosed in the patentliterature for the preparation of primary amines by the hydrogenation ofnitrites are as follows:

-   -   (i) Ammonia has to be used to decrease the selectivity of        secondary and tertiary amines.    -   (ii) Despite the improved selectivity to primary amine achieved        by the addition of an alkali metal hydroxide or carbonate, the        controlled and reproducible interaction between the additive and        the catalyst cannot be guaranteed.    -   (iii) As far as the alkali metal compound additive is used in        comparable amount to the catalyst the presence of certain        quantity of water in the reaction mixture is required. This        makes the reuse of catalyst and the separation of reaction        products more difficult.

Drawbacks (ii) and (iii) are also related to the process for theproduction of secondary amine from an alcohol and a primary amine over asupported nickel catalyst and in the presence of large amount of alkalimetal carbonate added to the reaction mixture (U.S. Pat. No. 5,254,736and EP Pat. No. 0 526 318).

The goal of this invention is to overcome the above drawbacks related toprevious processes disclosed for the preparation of primary amines bythe catalytic hydrogenation of nitrites. Thus the goal is to suppressthe secondary and tertiary amine formation in the hydrogenation ofnitrites to primary amines. The invention also aims at omitting ammoniaor keeping its partial pressure as low as possible in the nitrilehydrogenation process.

It has been found that, surprisingly, in the hydrogenation of nitrites,for example fatty acid nitrites such as lauronitrile, in the absence ofammonia, alkali metal carbonate or hydrogencarbonate, especially K₂CO₃,is the best modifier of the hydrogenation catalyst for suppressing theselectivity for the secondary amine to at most 2%. The low selectivityfor the secondary amine is maintained using an alkali metal carbonate orhydrogencarbonate up to a nitrile conversion of 99%. The modification ofthe hydrogenation catalyst using the alkali metal carbonate orhydrogencarbonate, such as K₂CO₃ or KHCO₃, may be carried out in aslurry using distilled water as the solvent.

The present invention thus provides a process for preparing a primaryamine by hydrogenating nitrites, in which a reaction mixture whichcomprises

-   -   (a) at least one nitrile,    -   (b) hydrogen,    -   (c) optionally ammonia and    -   (d) at least one cobalt or nickel catalyst modified ex situ by        adsorption of an alkali metal carbonate or alkali metal        hydrogencarbonate is converted.

The invention further provides a modified cobalt or nickel catalystobtainable by adsorption of an alkali metal carbonate or alkali metalhydrogencarbonate on a customary cobalt or nickel catalyst. Particularpreference is given to Raney nickel catalysts.

The modification of the catalyst is effected using alkali metalcarbonate or hydrogencarbonate. Useful alkali metals are Na, K, Rb, Cs.Preference is given to the alkali metal carbonates, and also inparticular K₂CO₃ or KHCO₃. The adsorption is effected from a solution ofthe alkali metal carbonates or hydrogencarbonates having concentrationsof preferably from 10 g/l up to 400 g/l. Preference is given toadsorption from aqueous solution, especially aqueous solution havingconcentrations of from 50 to 200 g/l.

Here, ex situ means that the catalyst has been modified outside,especially before, the hydrogenation reaction of nitrile to give aminewhich is catalyzed by it.

The weight ratio of dry catalyst to the solution of alkali metalcarbonate or hydrogencarbonate is preferably from 50 to 350 g/l.

The untreated catalyst is preferably cobalt, nickel, Raney cobalt orRaney nickel. The catalysts may be used without or with promoters.Promoters are, for example, Fe, Mo, Cr, Ti, Zr. The catalysts may beapplied to support materials. Such support materials are, for example,SiO₂, Al₂O₃, ZrO₂, MgO, MnO, ZnO, Cr₂O₃.

Particularly preferred embodiments are

-   -   Raney nickel without promoters, or with the promoters Fe, Mo,        Cr, Ti, Zr    -   nickel on the support materials SiO₂, Al₂O₃, ZrO₂, MgO, MnO,        ZnO, Cr₂O₃,    -   Raney cobalt without promoters, or with the promoters Ni, Cr    -   cobalt on the support materials SiO₂, Al₂O₃, MgO, MnO.

The untreated catalyst is preferably slurried in the solution of alkalimetal carbonate or hydrogencarbonate and stirred under hydrogen or aninert gas, for example nitrogen, for from about 1 to 16 hours.

The excess of the solution is removed after the adsorption by filtrationunder inert gas, preferably nitrogen atmosphere. It is advantageous towash the catalyst obtained after the adsorption with alcohol and thenwith a hydrocarbon.

In a preferred embodiment, the modified catalyst is obtained from theslurry by decanting and subsequently washing the catalyst three timeswith ethanol and twice with cyclohexane.

The alkali metal carbonate or hydrogencarbonates is present in themodified catalyst preferably in an amount of from about 2 to 12% byweight. In a particularly preferred embodiment, the modified catalystcontains K₂CO₃ or KHCO₃ in an amount of from about 6 to 7% by weight.

The process according to the invention is suitable for hydrogenating anynitrites. The nitrites are preferably of the formula R—CN where R is asaturated or unsaturated hydrocarbon group of from 1 to 32, preferablyfrom 4 to 24, in particular from 8 to 22, carbon atoms. R is alsopreferably an alkyl group, in particular linear alkyl group. Themodified catalyst is generally present in the reaction mixture in anamount of from 1 to 10% by weight based on the nitrile.

The reaction mixture may also contain a solvent. Suitable for thispurpose are preferably short-chain alcohols, especially methanol,ethanol and propanol, and also hydrocarbons such as hexane, cyclohexaneand toluene. The solvent may be present in the mixture in amounts offrom 0 to 90% by weight, based on the reaction mixture.

When ammonia is added to the reaction mixture, the amount of ammonia inthe reaction mixture should be from 1 to 10% by weight, based on thenitrile.

The nitrile hydrogenation over the modified catalyst is preferablycarried out under a hydrogen pressure of from 1 to 200 bar, inparticular from 2 to 30 bar.

The nitrile hydrogenation over the modified catalyst is preferablycarried out in the temperature range from 60 to 250° C., in particularfrom 100 to 150° C.

EXAMPLES

Catalyst Modification

The catalysts of Examples 1 to 14 are Raney nickel catalysts.

Example 1

2 g potassium carbonate were dissolved in 20 ml distilled water(concentration, c=100 g/l) and the 1.4 g wet (1 g dry) catalyst weresuspended in the solution and stirred at room temperature for 1 hour.After modification the suspension was decanted and the catalyst waswashed three times with 20 ml ethanol and twice with 20 ml cyclohexane.The potassium content of the catalyst was 2.4% by weight.

Example 2

3 g potassium carbonate were dissolved in 20 ml distilled water (c=150g/l) and the 1.4 g wet (1 g dry) catalyst were suspended in the solutionand stirred at room temperature for 1 hour. After modification thesuspension was decanted and the catalyst was washed three times with 20ml ethanol and twice with 20 ml cyclohexane. The potassium content ofthe catalyst was 3.2% by weight.

Example 3

4 g potassium carbonate were dissolved in 20 ml distilled water (c 32200 g/l) and the 1.4 g wet (1 g dry) catalyst were suspended in thesolution and stirred at room temperature for 1 hour. After modificationthe suspension was decanted and the catalyst was washed three times with20 ml ethanol and twice with 20 ml cyclohexane. The potassium content ofthe catalyst was 4.1 % by weight.

Example 4

8 g potassium carbonate were dissolved in 20 ml distilled water (c=400g/l) and the 1.4 g wet (1 g dry) catalyst were suspended in the solutionand stirred at room temperature for 1 hour. After modification thesuspension was decanted and the catalyst was washed three times with 20ml ethanol and twice with 20 ml cyclohexane. The potassium content ofthe catalyst was 4.6% by weight.

Example 5

3 g potassium carbonate were dissolved in 20 ml distilled water (c=150g/l) and the 1.4 g wet (1 g dry) catalyst were suspended in the solutionand stirred at room temperature for 1 hour. After modification thesuspension was decanted. The potassium content of the catalyst was 7.1 %by weight.

Example 6

3 g potassium carbonate were dissolved in 20 ml distilled water (c=150g/l) and the 1.4 g wet (1 g dry) catalyst were suspended in the solutionand stirred at room temperature for 1 hour. After modification thesuspension was filtered off under a nitrogen atmosphere. The potassiumcontent of the catalyst was 3.2% by weight.

Example 7

3 g potassium carbonate were dissolved in 20 ml distilled water (c=150g/l) and the 1.4 g wet (1 g dry) catalyst were suspended in the solutionand stirred at room temperature for 16 hours under a nitrogenatmosphere. After modification the suspension was decanted and thecatalyst was washed three times with 20 ml ethanol and twice with 20 mlcyclohexane. The potassium content of the catalyst was 3.3% by weight.

Example 8

1.3 g potassium carbonate were dissolved in 5 ml distilled water (c=150g/l) and the 1.4 g wet (1 g dry) catalyst were suspended in the solutionand stirred at room temperature for 1 hour. After modification thesuspension was decanted and the catalyst was washed three times with 20ml ethanol and twice with 20 ml cyclohexane. The potassium content ofthe catalyst was 3.1 % by weight.

Example 9

4 kg potassium carbonate were dissolved in 28 l distilled water (c=143g/l) and the 2 kg wet (1.4 kg dry) catalyst were suspended in thesolution and stirred at room temperature under a nitrogen atmosphere for2 hours. After 20 hours the catalyst settled down and the excess ofpotassium carbonate solution was removed by vacuum. The catalyst wasstored under a thin layer of potassium carbonate solution. Prior to usethe suspension was decanted and the catalyst was washed three times with20 ml ethanol and twice with 20 ml cyclohexane. The potassium content ofthe catalyst was 3.8% by weight.

Example 10

140 g potassium carbonate were dissolved in 610 ml distilled water(c=229 g/l alkali metal carbonate solution) and the 300 g wet (210 gdry) catalyst were suspended in the solution and stirred at roomtemperature under a nitrogen atmosphere for 2 hours. After modificationthe catalyst settled down overnight and the excess of solution wasremoved by vacuum. The modified Raney nickel catalyst was filtered offunder nitrogen. The potassium content of the catalyst was 3.9% byweight.

Example 11

3 g potassium hydrogencarbonate were dissolved in 20 ml distilled water(c=150 g/l) and the 1.4 g wet (1 g dry) catalyst were suspended in thesolution and stirred at room temperature for 1 hour. After modificationthe suspension was decanted and the catalyst was washed three times with20 ml ethanol and twice with 20 ml cyclohexane. The potassium content ofthe catalyst was 2.3% by weight.

Example 12

3 g sodium carbonate were dissolved in 20 ml distilled water (c=150 g/l)and the 1.4 g wet (1 g dry) catalyst were suspended in the solution andstirred at room temperature for 1 hour. After modification thesuspension was decanted and the catalyst was washed three times with 20ml ethanol and twice with 20 ml cyclohexane. The sodium content of thecatalyst was 2.4% by weight.

Example 13

3 g rubidium carbonate were dissolved in 20 ml distilled water (c=150g/l) and the 1.4 g wet (1 g dry) catalyst were suspended in the solutionand stirred at room temperature for 1 hour. After modification thesuspension was decanted and the catalyst was washed three times with 20ml ethanol and twice with 20 ml cyclohexane. The rubidium content of thecatalyst was 4.8% by weight.

Example 14

3 g cesium carbonate were dissolved in 20 ml distilled water (c=150 g/lalkali metal carbonate solution) and the 1.4 g wet (1 g dry) catalystwere suspended in the solution and stirred at room temperature for 1hour. After modification the suspension was decanted and the catalystwas washed three times with 20 ml ethanol and twice with 20 mlcyclohexane. The cesium content of the catalyst was 5.9% by weight.

Example 15

30 g potassium carbonate were dissolved in 200 ml distilled water (c=150g/l). 10 g dry nickel catalyst on SiO₂ (kieselguhr)/MgO (pulverulent Ni55/5 TS from Celanese) were suspended in the solution and stirred atroom temperature for 1 hour. After modification the suspension wasdecanted, the catalyst was washed five times with 20 ml ethanol anddried by vacuum. The potassium content of the catalyst was 3% by weight.

Example 16

30 g potassium carbonate were dissolved in 200 ml distilled water (c=150g/l). 10 g dry nickel catalyst on kieselguhr/Al₂O₃ (pulverulent Ni 62/15TS from Celanese) were suspended in the solution and stirred at roomtemperature for 1 hour. After modification the suspension was decanted,the catalyst was washed five times with 20 ml ethanol and dried byvacuum. The potassium content of the catalyst was 3.5% by weight.

Example 17

30 g potassium carbonate were dissolved in 200 ml distilled water (c=150g/l). 10 g dry cobalt catalyst on kieselguhr (pulverulent Co 45/20 TSfrom Celanese) were suspended in the solution and stirred at roomtemperature for 1 hour. After modification the suspension was decanted,the catalyst was washed five times with 20 ml ethanol and dried byvacuum. The potassium content of the catalyst was 3.3% by weight.

Example 18

30 g potassium carbonate were dissolved in 200 ml distilled water (c=150g/l). 14 g wet Raney cobalt catalyst B 2112 Z were suspended in thesolution and stirred at room temperature for 1 hour. After modificationthe suspension was decanted and the catalyst pressure-filtered undernitrogen. The potassium content of the catalyst was 3% by weight. TABLE1 Modified catalysts Alkali metal content of Example Modifier Catalystthe catalyst, % by wt. 1 Potassium carbonate Raney nickel 2.4 2Potassium carbonate Raney nickel 3.2 3 Potassium carbonate Raney nickel4.1 4 Potassium carbonate Raney nickel 4.6 5 Potassium carbonate Raneynickel 7.1 6 Potassium carbonate Raney nickel 3.2 7 Potassium carbonateRaney nickel 3.3 8 Potassium carbonate Raney nickel 3.1 9 Potassiumcarbonate Raney nickel 3.8 10 Potassium carbonate Raney nickel 3.9 11Potassium Raney nickel 2.3 hydrogencarbonate 12 Sodium carbonate Raneynickel 2.4 13 Rubidium carbonate Raney nickel 4.8 14 Cesium carbonateRaney nickel 5.9 15 Potassium carbonate Nickel 3 16 Potassium carbonateNickel 3.5 17 Potassium carbonate Cobalt 3.3 18 Potassium carbonateRaney cobalt 3Hydrogenation of NitrileControl Example 19 (Not an Example of this Invention)

A 300 ml stainless steel reactor was charged with 100 ml (0.447 mol)lauronitrile, and 1.4 g wet unmodified Raney nickel catalyst. Thereaction was run under 10 bar hydrogen pressure at 125° C. for 2 hours,and the reaction mixture was stirred at a rate of 1500 rpm. The yield ofdodecylamine was 83.2% at a conversion of 99.7%.

Example 20 (Not an Example of this Invention)

The reactor was charged with 100 ml (0.447 mol) lauronitrile, 1.4 g wetunmodified Raney nickel catalyst, and 2.28 g (0.134 mol) ammonia. Thereaction was run under 10 bar hydrogen pressure at 125° C. for 4 hours,and the reaction mixture was stirred at a rate of 1500 rpm. The yield ofdodecylamine was 93.6% at a conversion of 99.8%.

Example 21

A reactor was charged with 100 ml lauronitrile, and 1.4 g wet Raneynickel catalyst modified with 150 g/l K₂CO₃ solution as given in Example2. The reaction was run under 10 bar hydrogen pressure at 125° C. for 2hours, and the reaction mixture was stirred at 1500 rpm. The yield ofdodecylamine was 97.2% at a conversion of 99.8%.

Example 22

The reactor was charged with 100 ml lauronitrile, 1.4 g Raney nickelcatalyst modified with 150 g/l K₂CO₃ solution (Example 2), and 2.28 g(0.134 mol) ammonia. The reaction was run under 10 bar hydrogen pressureat 125° C. for 2 hours, and the reaction mixture was stirred at a rateof 1500 rpm. The yield of dodecylamine was 99.4% at a conversion of99.6%.

Example 23

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 100 g/l K₂CO₃ solution as given in Example 1.The yield of dodecylamine was 95.9% at 2 hours reaction time and aconversion of 99.9%.

Example 24

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 200 g/l K₂CO₃ solution as given in Example 3.The yield of dodecylamine was 91.0% at 2 hours reaction time and aconversion of 93.0%.

Example 25

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 400 g/l K₂CO₃ solution as given in Example 4.The yield of dodecylamine was 68.3% at 2 hours reaction time and aconversion of 69.9%.

Example 26

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 150 g/l K₂CO₃ solution as given in Example 5.The yield of dodecylamine was 60.5% at 4 hours reaction time and aconversion of 61.7%.

Example 27

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 150 g/l K₂CO₃ solution as given in Example 6.The yield of dodecylamine was 95.8% at 2 hours reaction time and aconversion of 99.8%.

Example 28

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 150 g/l K₂CO₃ solution as given in Example 7.The yield of dodecylamine was 96.1% at 2 hours reaction time and aconversion of 99.5%.

Example 29

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 150 g/l K₂CO₃ solution as given in Example 8.The yield of dodecylamine was 95.4% at 2 hours reaction time and aconversion of 99.9%.

Example 30

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 143 g/l K₂CO₃ solution as given in Example 9.The yield of dodecylamine was 92.3% at 2 hours reaction time and aconversion of 94.3%.

Example 31

A reactor was charged with 20 ml lauronitrile, 80 ml cyclohexane, and1.4 g Raney nickel catalyst modified with 150 g/l K₂CO₃ solution. Thereaction was run under 10 bar hydrogen pressure at 125° C., and thereaction mixture was stirred at 1500 rpm. The conversion of lauronitrilewas 99.6% and the yield of dodecylamine was 95.0%.

Example 32

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 100 g/l KHCO₃ solution as given in Example11. The yield of dodecylamine was 93.6% at 1 hour reaction time and aconversion of 99.4%.

Example 33

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 100 g/l Na₂CO₃ solution as given in Example12. The yield of dodecylamine was 84.2% at 1 hour reaction time and aconversion of 98.9%.

Example 34

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 150 g/l Rb₂CO₃ solution as given in Example13. The yield of dodecylamine was 96.3% at 2 hours reaction time and aconversion of 99.7%.

Example 35

The procedure of Example 21 was repeated except that the Raney nickelcatalyst was modified with 150 g/l Cs₂CO₃ solution as given in Example14. The yield of dodecylamine was 97.3% at 2 hours reaction time and aconversion of 99.2%.

Example 36

The reactor was charged with 100 ml lauronitrile, 1 g nickel catalyst,modified with 150 g/l K₂CO₃ solution, on kieselguhr/MgO (Example 15) and2 g (0.12 mol) ammonia. The reaction was run under 15 bar hydrogenpressure at 125° C. for 3 hours, and the reaction mixture was stirred at1500 rpm. The yield of dodecylamine was 99.2% at a conversion of 99.5%.

Example 37

The reactor was charged with 100 ml oleonitrile, 1 g nickel catalyst,modified with 150 g/l K₂CO₃ solution, on kieselguhr/Al₂O₃ (Example 16)and 2 g (0.12 mol) ammonia. The reaction was run under 10 bar hydrogenpressure at 120° C. for 2 hours, and the reaction mixture was stirred at1500 rpm. The yield of primary amines (oleylamine) was 99.3% at aconversion of 99.7%.

Example 38

The reactor was charged with 100 ml oleonitrile, 1 g cobalt catalyst,modified with 150 g/l K₂CO₃ solution, on kieselguhr (Example 17) and 3 g(0.12 mol) ammonia. The reaction was run under 60 bar hydrogen pressureat 140° C. for 4 hours, and the reaction mixture was stirred at 1500rpm. The yield of primary amines (oleylamine) was 99.6% at a conversionof 99.8%.

Example 39

The reactor was charged with 100 ml lauronitrile, 1 g Raney cobaltcatalyst modified with 150 g/l K₂CO₃ solution (Example 18) and 2 g (0.12mol) ammonia. The reaction was run under 50 bar hydrogen pressure at160° C. for 4 hours, and the reaction mixture was stirred at 1500 rpm.The yield of dodecylamine was 98.8% at a conversion of 99.2%. TABLE 2Results of the hydrogenation Example Catalyst Ammonia Conversion, %Selectivity, % Amine 19 (C) Raney nickel no 99.7 83.2 Dodecylamine 20(C) Raney nickel yes 99.8 93.6 Dodecylamine 21 Raney nickel no 99.8 97.2Dodecylamine 22 Raney nickel yes 99.6 99.4 Dodecylamine 23 Raney nickelno 99.9 95.9 Dodecylamine 24 Raney nickel no 93.0 91.0 Dodecylamine 25Raney nickel no 69.9 68.3 Dodecylamine 26 Raney nickel no 61.7 60.5Dodecylamine 27 Raney nickel no 99.8 95.8 Dodecylamine 28 Raney nickelno 99.5 96.1 Dodecylamine 29 Raney nickel no 99.9 95.4 Dodecylamine 30Raney nickel no 94.3 92.3 Dodecylamine 31 Raney nickel no 99.6 95.0Dodecylamine 32 Raney nickel no 99.4 93.6 Dodecylamine 33 Raney nickelno 98.9 84.2 Dodecylamine 34 Raney nickel no 99.7 96.3 Dodecylamine 35Raney nickel no 99.2 97.3 Dodecylamine 36 Nickel yes 99.5 99.2Dodecylamine 37 Nickel yes 99.7 99.3 Oleylamine 38 Cobalt yes 99.8 99.6Oleylamine 39 Raney cobalt yes 99.2 98.8 Dodecylamine

Examples 40 to 43

The activity on repeated use of Raney nickel catalyst in thehydrogenation of lauronitrile was investigated.

The autoclave (volume 10 l) was charged with 5 kg lauronitrile, 100 gRaney nickel catalyst and optionally 250 g ammonia. The reaction wascarried out at 10 bar hydrogen, 125° C. and a stir rate of 1000 rpm. Thelauronitrile conversion and the selectivity for dodecylamine weredetermined at different reaction times by amounts of catalyst falling asa result of recycling and sampling losses. Measurements were carried outusing modified and unmodified catalyst. The catalyst was modified inaccordance with Example 10. TABLE 3 Hydrogenation of lauronitrile usingunmodified catalyst and without addition of ammonia (Example 41)Catalyst use Amount of No. catalyst g Reaction time h Conversion %Selectivity % 1 100 3.1 99.9 88.3 2 95 3.5 99.8 87.7 3 88 3.5 100 85.6 481 3.6 99.7 85.8 5 74 4.0 99.9 85.4

TABLE 4 Hydrogenation of lauronitrile with unmodified catalyst withaddition of ammonia (Example 42) Catalyst use Amount of No. catalyst gReaction time h Conversion % Selectivity % 1 100 3.7 100 97.6 2 94 5.292.9 93.7 3 84 6.1 85.7 94.5 4 73 7.8 92.4 96.0 5 65 9.5 73.2 95.9

TABLE 5 Hydrogenation of lauronitrile with modified catalyst withoutaddition of ammonia (Example 43) Catalyst use Amount of No. catalyst gReaction time h Conversion % Selectivity % 1 100 3.6 100 98.1 2 94 5.899.9 93.0 3 85 7.4 100 94.6 4 77 12.3 99.8 95.7 5 69 23.6 99.7 95.9

TABLE 6 Hydrogenation of lauronitrile with modified catalyst and withaddition of ammonia (Example 44) Catalyst use Amount of No. catalyst gReaction time h Conversion % Selectivity % 1 100 3.5 99.6 99.9 2 94 8.199.2 99.9 3 88 10.6 99.1 99.7 4 79 11.8 99.5 98.7 5 70 10.3 100 99.4

1. A process for preparing a primary amine, said process comprising hydrogenating a reaction mixture which comprises (a) at least one nitrile, (b) hydrogen, and (c) a modified catalyst comprising at least one cobalt or nickel catalyst which contains alkali metal carbonate or hydrogencarbonate in an amount of from 2 to 12% by weight wherein said modified catalyst is modified ex situ by adsorption of an alkali metal carbonate or alkali metal hydrogencarbonate.
 2. The process as claimed in claim 1, in which the modified catalyst is prepared using alkali metal carbonates or alkali metal hydrogencarbonates by adsorption from an aqueous solution having a concentration of from 10 g/l to 400 g/l.
 3. The process as claimed in claim 2, in which the aqueous solution comprises K₂CO₃ having a concentration in the range from 50 to 200 g/l.
 4. The process of claim 1 wherein the modified catalyst is a modified Raney nickel catalyst.
 5. The process of claim 1, wherein the nitrile is of the formula R—CN in which R is a hydrocarbon group having from 1 to 32 carbon atoms.
 6. The process of claim 1, in which the modified catalyst is present in the reaction mixture in an amount of from 1 to 10% by weight based on the nitrile.
 7. The process of claim 1, in which said process is carried out in the presence of ammonia in an amount of from 1 to 10% by weight based on the nitrile.
 8. The process of claim 1, in which said process is carried out in the presence of cyclohexane.
 9. The process of claim 1, in which said process is carried out under a hydrogen pressure of from 1 to 200 bar.
 10. The process of claim 1, in which said process is carried out in the temperature range of from 60 to 250° C.
 11. A modified cobalt or nickel catalyst obtained by adsorption of an alkali metal carbonate or alkali metal hydrogencarbonate in an amount of from 2 to 12% by weight on a customary cobalt or nickel catalyst.
 12. The modified catalyst as claimed in claim 11, wherein the nickel catalyst a Raney nickel catalyst.
 13. The process of claim 1, in which said process is carried out under a hydrogen pressure of from 2 to 30 bar.
 14. The process of claim 1, in which said process is carried out in the temperature range of from 100 to 1 50° C.
 15. The process of claim 1, wherein the reaction mixture further comprises ammonia. 